This invention relates to a process and a catalyst composition used in the process for the hydrotreatment of a heavy hydrocarbon feedstock. This invention also relates to a catalyst and process for the manufacture of a hydrocarbon product having a low concentration of nitrogen and sulfur. The invention further relates to a high activity hydrodesulfurization and hydrodenitrogenation catalyst, a method of making such high activity catalyst, and a process for hydrotreating a heavy hydrocarbon feedstock using the high activity hydrodesulfurization and hydrodenitrogenation catalyst.
The catalytic hydrotreatment of hydrocarbon feedstock to remove impurities such as sulfur, nitrogen, and metal compounds is a commonly used process to improve or upgrade such hydrocarbon feedstock. This treatment to remove sulfur and nitrogen from heavy hydrocarbon feedstock is necessary due to various environmental regulations implemented by the United States and other countries. For example, the maximum sulfur concentration in on-road diesel is 15 parts per million (ppm) in the United States. Other organizations are pushing for limits as low as 5 to 10 ppm sulfur in diesel.
In a typical hydrotreating process, the hydrocarbon feedstock is contacted with a hydrotreating catalyst in the presence of hydrogen under process conditions that provide for a treated hydrocarbon product. The hydrotreating catalysts used in these processes generally are composed of an active phase that can include a component from the Group 6 metals and a component from the Group 10 metals supported on a porous, refractory inorganic oxide material.
The hydrotreatment of heavy hydrocarbon feedstock is particularly difficult because such feeds tend to have high concentrations of contaminating sulfur and nitrogen compounds and may require the use of more severe process conditions than those needed to treat lighter hydrocarbon feedstock. As the quality of feedstock declines reaction conditions tend to become more severe (e.g., increased temperatures or pressures) which increases production costs and causes more rapid depletion of catalyst activity. Thus, there is a continuing need for improving catalyst performance to offset the decreasing quality of feedstock and the increased processing costs associated therewith. In particular, the ability of a catalyst to achieve acceptable sulfur and nitrogen removal at lower temperatures is quite valuable because lower temperatures require less energy input which directly reduces production costs.
A conventional hydrodesulfurization/hydrodenitrogenation process is typically carried out by contacting the hydrocarbon feedstock with a hydrotreating catalyst in the presence of hydrogen at an elevated temperature and pressure. A typical hydrotreating catalyst contains a Group 6 metal component, such as molybdenum, and a Group 9 or Jo Group 10 component, such as cobalt or nickel, supported on a refractory oxide support.
One early patent, U.S. Pat. No. 3,669,904, discusses a method of making a gas oil hydrodesulfurization catalyst prepared from a precursor mixture of mildly calcined boehmite and uncalcined boehmite. The disclosed method addresses certain of the disadvantages and limitations with the use of technical grade boehmite in forming extruded pellets for use in making certain catalysts.
U.S. Pat. No. 3,853,789 discusses a method of making a mechanically strong alumina extrudate that may be used as a catalyst carrier. The extrudate is prepared by mixing water with specific proportions of gamma alumina powder having a certain particle size and alumina monohydrate (boehmite) having a certain particle size to form an extrudable paste from which an extrudate is formed. The extrudate is dried and then heat-treated at temperatures of 1150° to 1250° F. (621° to 677° C.).
U.S. Pat. No. 4,066,574 discusses a catalyst for use in the hydrodesulfurization of a heavy oil feedstock. The catalyst is an alumina support that is impregnated with Group 6 and Group 10 metals or metal compounds. The alumina support has a specific pore structure that provides for certain desired catalyst properties. The alumina support is made by mixing water and a strong mineral acid with amorphous or crystalline hydrate alumina powder to form a paste that is extruded. The density of the extrudate may be controlled by the addition of ammonium hydroxide to the extrudable paste. The extrudate is calcined at a temperature of 500° to 1600° F. (260° to 871° C.). The support has at least 70 volume percent of its pore volume in pores having a diameter between 80 Å and 150 Å and less than 3 volume percent of its pore volume in pores having a diameter above 1000 Å.
U.S. Pat. No. 4,089,811 discusses a method of making an alumina catalyst support by calcining alpha alumina monohydrate (boehmite) at a temperature of from about 800° to 900° F. (426° to 482° C.) to form calcined alumina containing gamma alumina and mixing the calcined alumina with water to form a wetted alumina. The wetted alumina at a pH of from 6 to 12.5 is heated to a temperature of from 190° to 250° F. (88° to 121° C.) for from 8 to 24 hours to convert the calcined alumina to beta alumina trihydrate.
U.S. Pat. No. 4,271,042 discusses a desulfurization catalyst comprising a hydrogenation catalytic component composited with gamma alumina that contains dispersed delta and/or theta phase alumina. The catalyst is prepared by precalcining gamma alumina or boehmite at a temperature of from 1600° to 2000° F. (871° to 1093° C.) to induce the formation of delta and/or theta phase alumina. The resulting powder is then mixed with alpha alumina monohydrate (boehmite) and formed into pellets or extrudates that are calcined at a temperature of from 900° to 1400° F. (482° to 760° C.) to form a catalyst support consisting of an intimate mixture of gamma alumina with delta and/or theta phase alumina.
U.S. Pat. No. 5,300,217 discusses a hydroprocessing catalyst that comprises a hydrogenation component supported on a porous, amorphous refractory oxide containing delta alumina. The amorphous, porous refractory oxide support material is prepared by extruding a precursor of the desired support, such as a refractory gel, followed by calcination of the extrudate. To obtain the desired delta-gamma alumina combination for the support, it is precalcined, prior to impregnation with the hydrogenation component, at a temperature above about 900° F. (482° C.) and preferably above 1800° F. (982° C.).
U.S. Pat. No. 7,790,652 discusses a catalyst for the hydroconversion of pitch. The catalyst comprises an alumina support material having a defined pore size distribution. The alumina support material is preferably prepared from a two-step precipitation process. The catalyst composition also comprises a Group 6 and Group 10 metal component. The overall catalyst composition exhibits high pitch conversion activity.
Published U.S. Patent Application 2006/0060510 discusses a high activity hydrodesulfurization catalyst. The catalyst comprises a support particle of gamma-alumina having a defined pore size distribution and crystalline structure. The catalyst also